While RestfulX currently lacks AMF support it definitely makes up for it by handling a considerable amount of the xml conversion that one would normally have to go through running a Flex app on top of Rails via HTTP/XML.  I’ve encountered a few quirks so far with the way data is loading that I’m working through with one of the developers on the project, however I feel that most of this will be resolved as the framework matures.

In the meantime I’ve started looking into alternative solutions for getting Flex running on top of Rails which has taken me down a few different paths such as using Cairngorm on top of a standard XML service as well as looking into WebOrb and RubyAMF to get binary AMF support which have various benefits when moving data across the wire to Flex.

WebOrb had alot of press early on when I first started with Ruby and while I’ve heard some good things about it, it doesn’t seem that it has been updated in a while.  It also seemed to have the least amount of interest based on the activity in their forums compared to the alternatives.

RubyAMF seems to be regularly updated, pretty well supported and has alot of helpful generators that will create some more of the mundane stuff (class mappings, amf based controllers, etc) for you.  I’ve had great luck getting this up and running and so far this has been my top choice for Flex on Rails development.  I will probably be posting a tutorial on getting Cairngorm talking with RubyAMF soon but until then you can look at these tutorials to point yourself in the right direction.

http://biemond.blogspot.com/2008/09/associations-with-ruby-on-rails-flex.html

http://panscendo.com/beginners-tutorial-to-rubyamf-with-restful-rails/